/*
 * $RCSfile: Vector2d.java,v $
 *
 * Copyright 1998-2008 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * $Revision: 1.5 $
 * $Date: 2008/02/28 20:18:51 $
 * $State: Exp $
 */

package etrl.vecmath;

import java.lang.Math;

/**
 * A 2-element vector that is represented by double-precision floating point x,y
 * coordinates.
 * 
 */
public class Vector2d extends Tuple2d implements java.io.Serializable {

	// Combatible with 1.1
	static final long serialVersionUID = 8572646365302599857L;

	/**
	 * Constructs and initializes a Vector2d from the specified xy coordinates.
	 * 
	 * @param x
	 *          the x coordinate
	 * @param y
	 *          the y coordinate
	 */
	public Vector2d(double x, double y) {
		super(x, y);
	}

	/**
	 * Constructs and initializes a Vector2d from the specified array.
	 * 
	 * @param v
	 *          the array of length 2 containing xy in order
	 */
	public Vector2d(double[] v) {
		super(v);
	}

	/**
	 * Constructs and initializes a Vector2d from the specified Vector2d.
	 * 
	 * @param v1
	 *          the Vector2d containing the initialization x y data
	 */
	public Vector2d(Vector2d v1) {
		super(v1);
	}

	/**
	 * Constructs and initializes a Vector2d from the specified Vector2f.
	 * 
	 * @param v1
	 *          the Vector2f containing the initialization x y data
	 */
	public Vector2d(Vector2f v1) {
		super(v1);
	}

	/**
	 * Constructs and initializes a Vector2d from the specified Tuple2d.
	 * 
	 * @param t1
	 *          the Tuple2d containing the initialization x y data
	 */
	public Vector2d(Tuple2d t1) {
		super(t1);
	}

	/**
	 * Constructs and initializes a Vector2d from the specified Tuple2f.
	 * 
	 * @param t1
	 *          the Tuple2f containing the initialization x y data
	 */
	public Vector2d(Tuple2f t1) {
		super(t1);
	}

	/**
	 * Constructs and initializes a Vector2d to (0,0).
	 */
	public Vector2d() {
		super();
	}

	/**
	 * Computes the dot product of the this vector and vector v1.
	 * 
	 * @param v1
	 *          the other vector
	 */
	public final double dot(Vector2d v1) {
		return (this.x * v1.x + this.y * v1.y);
	}

	/**
	 * Returns the length of this vector.
	 * 
	 * @return the length of this vector
	 */
	public final double length() {
		return (double) Math.sqrt(this.x * this.x + this.y * this.y);
	}

	/**
	 * Returns the squared length of this vector.
	 * 
	 * @return the squared length of this vector
	 */
	public final double lengthSquared() {
		return (this.x * this.x + this.y * this.y);
	}

	/**
	 * Sets the value of this vector to the normalization of vector v1.
	 * 
	 * @param v1
	 *          the un-normalized vector
	 */
	public final void normalize(Vector2d v1) {
		double norm;

		norm = (double) (1.0 / Math.sqrt(v1.x * v1.x + v1.y * v1.y));
		this.x = v1.x * norm;
		this.y = v1.y * norm;
	}

	/**
	 * Normalizes this vector in place.
	 */
	public final void normalize() {
		double norm;

		norm = (double) (1.0 / Math.sqrt(this.x * this.x + this.y * this.y));
		this.x *= norm;
		this.y *= norm;
	}

	/**
	 * Returns the angle in radians between this vector and the vector parameter;
	 * the return value is constrained to the range [0,PI].
	 * 
	 * @param v1
	 *          the other vector
	 * @return the angle in radians in the range [0,PI]
	 */
	public final double angle(Vector2d v1) {
		double vDot = this.dot(v1) / (this.length() * v1.length());
		if (vDot < -1.0)
			vDot = -1.0;
		if (vDot > 1.0)
			vDot = 1.0;
		return ((double) (Math.acos(vDot)));

	}

}
